Using the Exchange Control Panel we will select the option to upgrade distribution lists to Office 365 groups. You can select the GET STARTED option in UPGRADE DISTRIBUTION GROUPS or select the new upgrade icon in the group creation toolbar.

When the upgrade option is selected a new window is presented to select distribution groups for upgrade.

If we select all of the distribution lists for upgrade at once we can observe the number of upgrade operations that will occur in the lower left corner of the wizard.

In this instance only 499 distribution lists are selected but there are over 15,000 distribution lists that are eligible for upgrade. Why does this occur?

In the Exchange Control Panel the upgrade wizard performs a discover of distribution lists that is limited at 10,000 distribution groups. The service then performs eligibility checks against the 10,000 distribution lists that are selected and displays up to 499 eligible groups found within that group of 10,000. It is possible that the picker could display less than 499 – for example if out of the 10,000 we found only 200 that were eligible the wizard would only display 200. This means that there are distribution groups that could be eligible for upgrade that the picker will not display.

If the picker does not display the group for upgrade how does the group get upgraded? The first step is to reference the links previously posted in this blog. Administrators should execute the scripts attached to verify that the group has no upgrade blockers present. If the group has no upgrade blockers present, and the group does not appear in the wizard for upgrade, Powershell must be utilized to perform the upgrade. The commands are documented in the articles previously linked in this blog. Here is an example:

Validate that the group exists as a universal group (legacy distribution list):

A legacy distribution group can also be updated using the new-UnifiedGroup command. In this example we will create a distribution group with new-distributionGroup.

PS C:\> New-DistributionGroup TestDLNew! Office 365 Groups are the next generation of distribution lists.Groups give teams shared tools for collaborating using email, files, a calendar, and more.You can start right away using the New-UnifiedGroup cmdlet.